During the temperate months of the year many pest populations in various areas of the United States reach levels causing severe problems. One pest, the mosquito, can be distracting, can cause bites which itch and in certain areas can be a vector for the spread of communicable diseases such as equine encephalitis, malaria, etc. Mosquito populations vary during temperate periods depending upon species, rainfall, temperature and other conditions. While the life span of an adult mosquito is not long, mosquito larva can continually mature throughout the year into the adult stage, resulting in the continuing resupply of the adult mosquito population. Further, due to the presence of a large variety of different mosquito species and differing maturation times and rates, mosquito pests can be present during much of the temperate season.
Many communities have combated mosquito populations and other pests by fogging or spraying the environment with an insecticide, adding insecticide to likely hatching sites, and by distributing a variety of immediate to slow release insecticide compositions into the environment. The treatment of large areas of the environment having significant numbers of trees, shrubs and other vegetation requires a particulate form of pest control agent to effectively control population. A pest control agent in the form of dense granules is preferred in aerial applications. Such dense granules permit accurate application of the pest control agent in winds up to 14 miles per hour. The dense granules permit penetration of dense vegetation canopies and reduce uneven application (drift) caused by variations in winds and turbulence. During the breeding season, dense granules can be used to regulate the rate of pesticide release in an environmental body of water over an extended period of time. In another environment, the pest control means can be applied to a dry site that experiences periodic flooding. The composite particle while wet can release significant proportions of pesticide.
Many other pests can cause severe problems during their growth or reproductive cycles. Such cycles generally correspond to the temperate seasons of the year and are often triggered by the presence of moisture. Mollusks in both the old and larva forms can infest fresh water damage flora and fauna, provide a diseased vector and impose cosmetic problems. Fungi and algae grow rapidly in fresh water and can make water unpleasant for recreational purpose, may produce toxins which poison farm animals and can make water unfit for human consumption. A variety of plants can grow in unwanted areas, reducing crop yields and presenting weed control problems in many residential and agricultural environments. Many attempts have been made to combat these pests with pest control devices using a variety of pesticides.
Pesticides have been encapsulated with both macro and microencapsulation processes, placed in ceramic materials, included in biodegradable polymers, mixed with porous mineral supports, coated with cellulosic derivatives, combined with polyuria compounds, and included with gypsum and other supports to protect the pesticide from the environment and to ensure a controlled release in an attempt to substantially control pest populations. Sjogren, U.S. Pat. No. 4,732,762, teaches a slow release pest control composition comprising an encapsulated pesticide, carbon and a plaster. The high compressive strength plaster causes a slow release of the materials into the environment. Sjogren, U.S. Pat. No. 4,971,796, teaches a layered pest control agent comprising a core particle and layered on the core particle, intermediate spacing layers of a proteinaceous layer and an intermediate spacing layer, the proteinaceous layer containing pesticide.
For the purpose of this invention, a pesticide is considered any material, compound, composition, bacteria, virus, or other chemical or bio-active material that can act to reduce populations of a pest in an infested locale. An effective pest control concentration is defined as a concentration effective to kill a substantial proportion of at least one stage or form of a pest during its life cycle, or a concentration effective to prevent the development or maturation of one or more stages of the pest during its life cycle. The pesticide should be released by the pest control means at a substantially even rate during a treatment, such that an effective concentration is released but the pesticide is not wasted. In areas of dense vegetation, the pest control means is preferably of small size, about 0.5 to 10 millimeters in diameter, to permit even distribution and penetration of dense vegetation in environmental areas where pest control applications are needed. The pest control means should have a density that permits easy penetration of dense vegetation and precise application even in high or variable wind conditions. The pesticide composition and means should comprise natural materials, be biodegradable and of low cost.
Accordingly, a substantial need exists for a controlled release pest control composition that can be made into a granular control means, can be supplied by aircraft or by hand or other machine broadcast techniques. A further need exists for a pest control agent that is of sufficient density to be easily applied to environmental locations, can be applied to either wet or dry locales but can release an effective pest control concentration of pesticide into environmental water. Still a further need exists for a pest control means that can provide substantial control of pest populations in a quick release mode, from 0.1 to 72 hours, an intermediate release, for 1-12 days, or in a long lasting slow release mode, for 10-30 days. Finally, a need exists for a granular pest control composition where significantly less materials per acre applied still results in substantial control of pest populations. The granule should protect the pesticide from substantial degradation, provide for uniform distribution of the pest control means and sustain controlled release of the pesticide in any environment.